Buyers are facing a competitive market in which they need to move quickly, bid high and make other concessions if they want to land the deal, real estate agents say. And for every month that buyers strike out, the combination of rising home prices and higher mortgage rates can add hundreds or thousands of dollars to the cost of the home.

Andrew Stubblebine, 29, decided to get serious about his home search this spring after seeing that mortgage rates were rising and that home prices in Seattle climbed by more than 14 percent over the past year.

“My buying power was eroding just from waiting,” said Stubblebine, an engineer who had browsed home listings casually for about a year. “It was almost depressing how much it was going up.”

The average rate for 30-year fixed mortgages reached 4.54 percent last week, up from an average of 3.89 percent a year ago, according to Freddie Mac, an entity started by Congress to help expand access to homeownership. Real estate agents and economists say rates are still low by historical standards, but they are expected to rise further if the Federal Reserve continues to boost interest rates. Fed officials bumped up the benchmark interest rate by 0.25 percentage points to a range of 1.75 percent to 2 percent at the end of Wednesday’s meeting.

Those increases are being rolled out against a backdrop of robust economic growth. The unemployment rate dropped to 3.8 percent last month, a level not seen since 2000. A decade after the start of the financial crisis, consumers are feeling more confident about their finances, and some people finally believe they have the means to enter the housing market.

Nearly half of the new mortgages issued by Freddie Mac in the first quarter went to first-time home buyers. That is up from 40 percent in the first quarter of 2015 and 33 percent in the first quarter of 2012.

Still, the average number of new and existing homes sold from January through April of this year fell by 1 percent, compared with the start of 2017, making it the first spring home-buying season since 2011 where sales didn’t grow from the year before.

“Home sales had been steadily improving slowly since the recession, and this year they’ve kind of gone sideways,” said Mark Zandi, chief economist for Moody’s Analytics.

Growth in the housing market has stalled as prospective buyers compete for a limited number of homes, Zandi said.

If sales continue at their current pace, the number of homes on the market as of mid-May would run out in 4.5 months, down slightly from 4.8 months last year, according to Pro Teck Valuation Services, a real estate analytics company. (Some real estate agents say there should be enough houses for sale to last about six months in a healthy market.)

The number of new homes under construction is also not enough to meet demand. About 900,000 new single family homes will be built this year, according to projections from the National Association of Home Builders, but that will fall short of the 1.2 million homes needed to keep up with population growth and to replace old housing, said Robert Dietz, chief economist for the association.

Construction of entry-level homes is especially low as developers focus on building larger, pricier homes to make up for higher costs, Dietz said. A tariff on Canadian lumber has helped push lumber prices up by more than 60 percent since the start of 2017, he said. Many developers are also limited in how much they can build by zoning laws that require a certain amount of land. Those factors, combined with rising land and labor costs, have steered builders to more expensive homes if they want to earn a profit, Dietz said.

In some competitive markets, sellers accept offers within a week of putting their homes up for sale. Real estate agents describe what has become a typical timeline: Homes are listed on a Wednesday or Thursday, open houses are held over the weekend, and offers are due the following Monday or Tuesday.

When Stubblebine found a townhouse he loved in mid-May, he knew he would have to move quickly to beat out other buyers in the popular downtown neighborhood.

After seeing the house on a Saturday, he took off work the following Monday to start on the paperwork and have the home pre-inspected. He made an offer on Tuesday that was 16 percent above the asking price and contained other items he thought would appeal to the seller, including waiving the contingencies for the inspection and financing.

That meant he agreed to be on the hook for the purchase amount even if his financing fell through.

He also waived the contingency for the property appraisal, which meant he would have to make up the difference if his lender found the home was worth less than the sale price. “I was very nervous after submitting the offer,” Stubblebine said. But about a week after he made the offer, the appraisal came back at above the sale price.

Compounding the shortage is a trend of people staying in their homes longer, for an average of 10 years as of 2017, up from six in 2008, according to the National Association of Realtors. Some owners find they cannot afford the larger homes in their neighborhoods, brokers say, so instead of moving out they are staying put and renovating, putting a damper on the amount of homes available for sale.

The housing crunch leads to a frustrating experience for buyers, said Lawrence Yun, chief economist of the National Association of Realtors. “They have to hurry the decision,” he said. “Maybe they have to offer full price. And after all this they might have to start again.”

Alex Woodruff, 26, learned during the first week of his housing search in December that he would have to act fast. A home that he considered making an offer on was taken off the market while he was thinking it over.

“Seeing places just get snatched up while I was looking, it was annoying,” he said.

In February he closed on a one-bedroom condo with exposed brick that was in his price range of about $200,000. He saw the home at the end of December and made an offer two days later, on New Year’s Day.

Woodruff said that in hindsight, the 4 percent rate he locked in on his 30-year mortgage in February was a pretty good deal. His girlfriend is shopping for homes now and was quoted a rate of about 4.3 percent. On a $200,000 home, that 0.3 percentage point difference on a 30-year mortgage can add $35 to the monthly mortgage costs, or almost $12,600 over the life of the loan.

Jonnelle MarteJonnelle Marte is a reporter covering personal finance. She was previously a writer for MarketWatch and the Wall Street Journal. Follow